JP7397736B2 - Etching method and substrate processing method - Google Patents

Description

The present invention includes, for example, semiconductor wafers, glass substrates for liquid crystal display devices, substrates for plasma displays, substrates for FED (Field Emission Display), substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, substrates for photomasks, The present invention relates to an etching method and a substrate processing method for processing substrates such as ceramic substrates and solar cell substrates.

As a semiconductor device and a method for manufacturing the same, Japanese Patent Application Publication No. 2018-195718 discloses a Fin Field Effect Transistor (FINFET) and a method for manufacturing the same. A FINFET has a fin formed on top of a substrate. In one step in the manufacturing method, a dummy gate electrode and sidewalls, and an interlayer insulating film covering them are formed on the fin. For example, a polysilicon layer, a silicon nitride layer, and a silicon oxide layer are used as the dummy gate electrode, sidewalls, and interlayer insulating film. In the subsequent process, an upper surface with exposed dummy gate electrodes, sidewalls, and interlayer insulating film is formed by CMP (Chemical Mechanical Polishing). At this point, a stack of silicon oxide layers and silicon nitride layers stacked on each other in the in-plane direction (direction parallel to the top surface) and a polysilicon layer adjacent thereto are present on the substrate at this point. Note that the laminate was partially removed by the CMP action (chemical action and mechanical action). In the subsequent step, wet etching is performed to remove the polysilicon layer while leaving this stack (ie, silicon nitride layer and silicon oxide layer).

JP 2018-195718 Publication

The wet etching described above requires high etching selectivity. Specifically, when removing polysilicon, it is required to suppress the amount of etching of the stack of silicon oxide layers and silicon nitride layers, that is, the amount of loss. If the amount of loss is large, the stacked body will be severely eroded, and the more integrated the semiconductor device is, the greater the adverse effect will be. With the recent progress in integration, there is a strong need to reduce the amount of loss. However, after the process of partially removing the stack by CMP (more generally, a process that has physical and/or chemical effects), the stack of silicon oxide and silicon nitride layers is removed. When wet etching is performed to selectively remove polysilicon from an object to be processed including a polysilicon layer, it has been difficult to sufficiently reduce the amount of loss.

Similar to this, high etching properties are sometimes required for wet etching in recesses formed by etching in a stack of silicon oxide layers and polysilicon layers. Specifically, when removing polysilicon, it may be required to suppress the amount of the silicon oxide layer that is etched, that is, the amount of loss. If the amount of loss is large, the silicon oxide layer will be severely eroded, and the more integrated the semiconductor device is, the greater the adverse effect will be. With the recent progress in integration, there is a strong need to reduce the amount of loss. However, when wet etching is performed to selectively remove polysilicon in the recesses after forming recesses in a stack of silicon oxide layers and polysilicon layers by etching, the loss of the silicon oxide layer cannot be sufficiently reduced. It was difficult to reduce it.

Therefore, one object of the present invention is that wet etching for selectively removing polysilicon from a workpiece including a stack of silicon oxide layers and silicon nitride layers and a polysilicon layer can be performed using physical and chemical effects. An object of the present invention is to provide an etching method capable of suppressing the amount of loss of a laminate in wet etching when the laminate is partially removed by a process including at least one of the following.

Another object of the present invention is to form a recess in a stack of a silicon oxide layer and a polysilicon layer by etching, and then perform wet etching to selectively remove polysilicon in the recess. An object of the present invention is to provide a substrate processing method that can suppress the amount of layer loss.

A first aspect disclosed herein is a method of etching a workpiece including a stack of silicon oxide layers and silicon nitride layers, and a polysilicon layer, the method comprising: (a) physical action and chemical action; (b) a mixed aqueous solution of ammonium hydroxide and hydrogen peroxide, or tetramethylammonium hydroxide as a first etching solution; a step of exposing the object to be treated to a solution; (c) a step of exposing the object to ammonia as a second etching solution after step (b); and (d) a step of exposing the object to aqueous ammonia as a second etching solution. and then etching the polysilicon layer by exposing the object to be treated to a tetramethylammonium hydroxide solution as a third etching solution.

A second aspect disclosed in this specification is the etching method of the first aspect, in which the second etching solution has a temperature of 50° C. or more and 80° C. or less.

A third aspect disclosed herein is the etching method according to the first or second aspect, wherein the second etching solution contains ammonium hydroxide in a mass ratio of 3 to 10 times that of water. It is ammonia water dissolved in

A fourth aspect disclosed herein is directed to a substrate that includes a stack of a silicon oxide layer and a polysilicon layer, and has a recess formed in the stack by etching with generation of etching residue. The substrate processing method includes: the recess having an inner surface exposing the silicon oxide layer and the polysilicon layer; , a step of removing the etching residue adhering to the inner surface of the recess, and (b) supplying an ammonia aqueous solution into the recess after the step (a), thereby removing the etching residue at or before the step (a). (c) after the step (b), supplying a quaternary ammonium hydroxide solution into the recessed portion; a second etching step of etching the polysilicon layer at a higher etching rate than the silicon oxide layer.

A fifth aspect disclosed in the present specification is directed to a substrate including a laminate of a silicon oxide layer and a polysilicon layer, and having a recess formed in the laminate by etching with generation of etching residue. The substrate processing method includes: the recess having an inner surface exposing the silicon oxide layer and the polysilicon layer; , a step of removing the etching residue adhering to the inner surface of the recess, and (b) supplying an ammonia aqueous solution into the recess after the step (a), thereby removing the etching residue at or before the step (a). a first etching step of etching the surface oxide film formed on the polysilicon layer; and (c) after the step (b), using an ammonia aqueous solution having a higher ammonia concentration than the ammonia aqueous solution in the step (b). a second etching step of etching the polysilicon layer at a higher etching rate than the silicon oxide layer by supplying the polysilicon layer into the recess.

A sixth aspect disclosed in this specification is the substrate processing method according to the fourth or fifth aspect, in which the steps (a) to (c) are performed continuously.

According to the etching method of the first aspect, in step (b) performed prior to etching the polysilicon layer in step (d), the laminate is formed by a process having at least one of a physical action and a chemical action. The foreign matter generated when the is partially removed is removed. Furthermore, the natural oxide film of the polysilicon layer is removed in step (c), which is performed prior to etching the polysilicon layer in step (d). By removing the natural oxide film, the removal of the polysilicon layer is no longer inhibited by the natural oxide film, so that etching of the polysilicon layer proceeds efficiently. Therefore, the amount of loss in the laminate can be suppressed. Furthermore, since the above step (b) is performed before this step (c), the removal of the natural oxide film is not inhibited by the above foreign matter, so that the etching until the natural oxide film is removed can be carried out efficiently. proceed. Therefore, the amount of loss can be further suppressed. Furthermore, by using a tetramethylammonium hydroxide solution as an etching solution in step (d), polysilicon is etched with high selectivity. Therefore, the amount of loss can be further suppressed. From the above, wet etching for selectively removing a polysilicon layer from a workpiece including a stack of silicon oxide layers and silicon nitride layers and a polysilicon layer has at least one of a physical action and a chemical action. When the wet etching is performed after a step of partially removing the laminate, the amount of loss of the laminate during wet etching can be sufficiently suppressed.

According to the etching method of the second aspect, the second etching solution has a temperature of 50°C or more and 80°C or less. Since the second etching solution has a temperature of 50° C. or more, the natural oxide film of the polysilicon layer in step (c) can be easily removed in a short time as usually desired in mass production. When the second etching solution has a temperature of 80° C. or less, the second etching solution can be easily handled.

According to the etching method of the third aspect, the second etching solution is aqueous ammonia in which ammonium hydroxide is dissolved in water in a mass ratio of 3 to 10 times. Suppressing unintended damage in the above step (c) due to excessive ammonium hydroxide concentration by dissolving ammonium hydroxide in water at a mass ratio of 3 times or more. I can do it. Since ammonium hydroxide is dissolved in water at a mass ratio of 10 times or less, the natural oxide film of the polysilicon layer in step (c) can be easily removed in a short period of time as usually desired in mass production.

According to the substrate processing method of the fourth aspect, etching residues generated by etching are removed in step (a), which is performed prior to etching the polysilicon layer in step (c). Furthermore, the surface oxide film of the polysilicon layer is removed in step (b), which is performed prior to etching the polysilicon layer in step (c). By removing the surface oxide film, the removal of the polysilicon layer is no longer inhibited by the surface oxide film, so that etching of the polysilicon layer proceeds efficiently. Therefore, the amount of loss of the silicon oxide layer can be suppressed. Furthermore, since the above step (a) is performed before this step (b), the removal of the surface oxide film is not inhibited by etching residue, so that the etching until the surface oxide film is removed can be carried out efficiently. proceed. Therefore, the amount of loss can be further suppressed. Further, by using a quaternary ammonium hydroxide solution as an etching solution in step (c), polysilicon is etched with high selectivity. Therefore, the amount of loss can be further suppressed. From the above, when wet etching is performed to selectively remove polysilicon in the recesses after the process of forming recesses in a stack of silicon oxide layers and polysilicon layers by etching, the loss of the silicon oxide layer during wet etching The amount can be sufficiently suppressed.

According to the substrate processing method of the fifth aspect, etching residues generated by etching are removed in step (a), which is performed prior to etching the polysilicon layer in step (c). Furthermore, the surface oxide film of the polysilicon layer is removed in step (b), which is performed prior to etching the polysilicon layer in step (c). By removing the surface oxide film, the removal of the polysilicon layer is no longer inhibited by the surface oxide film, so that etching of the polysilicon layer proceeds efficiently. Therefore, the amount of loss of the silicon oxide layer can be suppressed. Furthermore, since the above step (a) is performed before this step (b), the removal of the surface oxide film is not inhibited by etching residue, so that the etching until the surface oxide film is removed can be carried out efficiently. proceed. Therefore, the amount of loss can be further suppressed. Furthermore, polysilicon can be etched sufficiently efficiently by using an ammonia aqueous solution having a higher ammonia concentration than the ammonia aqueous solution in the above step (b) as the etching solution in step (c). From the above, when wet etching is performed to efficiently and selectively remove polysilicon in the recesses after the process of forming recesses in a stack of silicon oxide layers and polysilicon layers by etching, the silicon oxide in wet etching The amount of layer loss can be sufficiently suppressed.

According to the substrate processing method of the sixth aspect, steps (a) to (c) are performed continuously, thereby making it possible to efficiently process the substrate. Since steps (a) to (c) are performed continuously in this way, a rinsing step cannot be interposed between the steps, but steps (a) to (c) all use an ammonia-based treatment liquid. Therefore, even if there is no rinsing step between the steps, the adverse effects from the previous step are small. Therefore, efficient substrate processing is realized as described above.

Objects, features, aspects, and advantages of the invention will become more apparent from the following detailed description and accompanying drawings.

1 is a partial plan view schematically showing the configuration of a semiconductor device in Embodiment 1. FIG. 2 is a schematic partial cross-sectional view along line II-II in FIG. 1; FIG. 2 is a flow diagram schematically showing a part of a method for manufacturing the semiconductor device of FIG. 1. FIG. 4 is a partial cross-sectional view schematically showing step S110 and step S120 in FIG. 3. FIG. 4 is a partial cross-sectional view schematically showing step S130 in FIG. 3. FIG. 4 is a partial cross-sectional view schematically showing step S140 in FIG. 3. FIG. 4 is a partial cross-sectional view schematically showing step S150 in FIG. 3. FIG. The relationship between the amount of polysilicon etched by ammonia water and the time is shown in the case of ammonium hydroxide:water = 1:5 and a temperature of 65°C, the case of ammonium hydroxide:water = 1:5 and a temperature of 40°C, and the case of etching time of polysilicon with ammonia water. FIG. 2 is a graph showing the results of an experiment in which ammonium oxide:water = 1:100 and a temperature of 65°C and ammonium hydroxide:water = 1:100 and a temperature of 40°C. FIG. 2 is a graph diagram showing the results of an experiment in which the relationship between the amount of etching of polysilicon (p-Si), silicon oxide (TEOS), and silicon nitride (SiN) by ammonia water and time was investigated. FIG. 2 is a graph showing the results of an experiment in which the relationship between etching amount and time of polysilicon (p-Si), silicon oxide (TEOS), and silicon nitride (SiN) using a tetramethylammonium hydroxide (TMAH) solution was investigated. FIG. 2 is a cross-sectional view schematically showing the configuration of a substrate processing apparatus in a second embodiment. FIG. 7 is a cross-sectional view schematically showing the configuration of a substrate before and after the substrate processing method in Embodiment 2 is performed. 7 is a flow diagram for explaining a substrate processing method in Embodiment 2. FIG.

Embodiments of the present invention will be described below based on the drawings. In the following drawings, the same or corresponding parts are given the same reference numerals and the description thereof will not be repeated.

<Embodiment 1>
FIG. 1 is a partial plan view schematically showing the configuration of a FINFET 190 (semiconductor device) in the first embodiment, and FIG. 2 is a schematic partial cross-sectional view taken along line II-II (FIG. 1). The FINFET 190 includes a substrate 110 having a base portion 111 and a fin portion 112, an insulated gate structure 130 having a gate insulating film 131 and a gate electrode 132, a TEOS layer 150 (silicon oxide layer) as an interlayer insulating film, and an insulated gate structure 130. It has a SiN layer 140 (silicon nitride layer) as a sidewall.

The fin portion 112 is a fin-shaped portion on the base portion 111 of the substrate 110. Specifically, the fin portion 112 protrudes upward (upward in FIG. 2) from the base portion 111 (FIG. 1) along the thickness direction. Further, the fin portion 112 extends in the in-plane direction (lateral direction in FIGS. 1 and 2). The fin portion 112 may have an upper surface that is approximately parallel to the in-plane direction, as shown in FIG. 2 .

Gate electrode 132 is made of metal. As shown in FIG. 1, the gate electrode 132 extends across the fin portion 112 on the substrate 110. At this intersection, the gate electrode covers not only the top surface of the fin portion 112 but also both side surfaces. Gate electrode 132 and substrate 110 are separated by gate insulating film 131.

The SiN layer 140 (sidewall) is placed on both sides of the gate electrode 132. The SiN layer 140 and the gate electrode 132 may be separated by a gate insulating film 131. The gate electrodes 132 adjacent to each other on the upper surface of the fin portion 112 are separated by a TEOS layer 150 as an interlayer insulating film in addition to the SiN layer 140 disposed on the side surface of each gate electrode 132. The TEOS layer is a silicon oxide layer formed by CVD (Chemical Vapor Deposition) using TEOS (Tetraethoxysilane) as a source gas.

A plurality of impurity regions 120 as a source region or a drain region are formed on the upper surface of the fin portion 112 (FIG. 2). Each impurity region 120 has a main portion 121 and an extension portion 122. The main portion 121 faces the bottom surface of the TEOS layer 150 (interlayer insulating film), and the extension portion 122 faces the bottom surface of the SiN layer 140 (sidewall).

FIG. 3 is a flow diagram schematically showing a portion of the method for manufacturing FINFET 190 (FIG. 2).

Referring to FIG. 4, in step S110 (FIG. 3), p-Si layer 160 (polysilicon layer) is formed on fin portion 112 as a dummy gate electrode. The planar layout of the p-Si layer 160 (dummy gate electrode) corresponds to the planar layout of the insulated gate structure 130 (FIG. 2). Note that the insulated gate structure 130 (FIG. 2) has not yet been formed at this point.

Next, extension portions 122 of impurity region 120 are formed by first ion implantation using p-Si layer 160 as a mask. Next, SiN layers 140 (sidewalls) are formed on both sides of the p-Si layer 160. Next, the main portion 121 of the impurity region 120 is formed by second ion implantation using the p-Si layer 160 provided with SiN layers 140 (sidewalls) on both sides as a mask. The second ion implantation is performed deeper than the first ion implantation. As a result, only both end portions of the extension portion 122 formed by the first ion implantation remain, and the central portion becomes the main portion 121 having a greater depth.

Next, in step S120 (FIG. 3), annealing is performed to activate impurity region 120. The annealing temperature is, for example, a high temperature of about 1000°C. Note that the p-Si layer 160 serving as the dummy gate electrode is made of polysilicon, unlike the gate electrode 132 (FIG. 2) made of metal, and therefore has sufficient heat resistance against the annealing temperature.

Referring to FIG. 5, in step S130 (FIG. 3), a TEOS layer 150 (interlayer An insulating film) is formed. Specifically, film formation is performed by a CVD method using TEOS as a source gas. In FIG. 5, a SiN layer 140 and a TEOS layer 150 are stacked in the X direction. In other words, a stacked body of the TEOS layer 150 and the SiN layer 140 is formed. This laminate and the p-Si layer 160 are also referred to as objects to be processed below. At this point, the object to be processed has an upper surface S1 consisting of the TEOS layer 150. This object to be processed is subjected to an etching process in a step to be described later.

Next, in step S140 (FIG. 3), the upper surface of the object to be processed is processed by CMP processing using slurry. The mechanical action (in other words, physical action) caused by the abrasive grains in the slurry and the chemical action caused by the chemicals in the slurry reach the upper surface of the workpiece, so that the upper surface changes from the upper surface S1 (FIG. 5). It is scraped to the upper surface S2 (FIG. 6). Specifically, the stacked body (TEOS layer 150 and SiN layer 140) is partially removed, and at the same time, the TEOS layer 150 (interlayer insulating film) is partially removed.

Next, in step S150 (FIG. 3), the p-Si layer 160 (FIG. 6) serving as a dummy gate electrode is removed as shown in FIG. Specifically, first to third wet etchings are performed in steps S151 to S153, respectively, as described below.

First, in step S151 (FIG. 3), first wet etching is performed by exposing the object to a first etching solution. For example, the first etching liquid is discharged from a shower nozzle onto the object to be processed. As the first etching solution, an aqueous mixed solution (SC1) of ammonium hydroxide (NH ₄ OH) and hydrogen peroxide (H ₂ O ₂ ) or a tetramethylammonium hydroxide (TMAH) solution is used. The components of SC1 may be commonly used components. The solvent of the TMAH solution may be water (H ₂ O), and for example, TMAH is dissolved in about 4 times as much water by mass.

Next, in step S152 (FIG. 3), second wet etching is performed by exposing the object to a second etching solution. For example, the second etching liquid is discharged from a shower nozzle onto the object to be processed. As the second etching solution, diluted ammonia water (dNH ₄ OH) is used. Note that the second etching solution has different components from those of the first etching solution. Therefore, the second etching solution is not SC1 and does not substantially contain hydrogen peroxide. The second etching solution preferably has a temperature of 50°C or more and 80°C or less. Further, the second etching solution is preferably ammonia water in which ammonium hydroxide is dissolved in water in a mass ratio of 3 times or more and 10 times or less.

In terms of processing efficiency, it is preferable that rinsing processing (cleaning processing) is not performed between step S151 and step S152. In other words, after the object to be processed is exposed to the first etching solution, it is preferable that the object is exposed to the second etching solution without being exposed to any other solution. Even if the rinsing treatment is omitted in this manner, since both the first etching liquid and the second etching liquid are ammonia-based etching liquids, no major problems regarding chemical reactions will substantially occur. Furthermore, if step S152 is performed in a single wafer type (by discharging the second etching liquid onto the object to be processed), or if it is a batch type (in which the object to be processed is immersed in the second etching liquid in an etching tank). Unlike the case where the first etching liquid is mixed into the etching tank of the second etching liquid, there is no problem of the first etching liquid getting mixed into the etching bath of the second etching liquid.

Next, in step S153 (FIG. 3), third wet etching is performed by exposing the object to a third etching solution. For example, the third etching liquid is discharged from a shower nozzle onto the object to be processed. This etches the p-Si layer 160. A TMAH solution is used as the third etchant. The solvent of the TMAH solution may be water (H ₂ O), and for example, TMAH is dissolved in about 4 times as much water by mass.

In terms of processing efficiency, it is preferable that rinsing processing (cleaning processing) is not performed between step S152 and step S153. In other words, after the object to be processed is exposed to the second etching liquid, it is preferable that the object is exposed to the third etching liquid without being exposed to any other liquid. Even if the rinsing treatment is omitted in this manner, no major problem regarding chemical reactions occurs because both the second etching liquid and the third etching liquid are ammonia-based etching liquids. Moreover, when step S153 is a single-wafer type, unlike the case of a batch type, there is no problem of the second etching solution getting mixed into the etching bath for the third etching solution.

Next, in step S160 (FIG. 3), the p-Si layer 160 (FIG. 6) as a dummy gate electrode is removed as shown in FIG. 2) is formed. This results in a FINFET 190.

In step S140 (FIG. 3) described above, when the stack of the TEOS layer 150 and the SiN layer 140 is partially removed by CMP using slurry (see FIGS. 5 and 6), the top surface S2 (FIG. ), slurry residue (foreign matter) that covers the p-Si layer 160 is likely to be formed. According to this embodiment, this foreign material is removed by the first wet etching (step S151: FIG. 3) performed prior to etching the p-Si layer 160 in the third wet etching (step S153: FIG. 3). Ru. Furthermore, the natural oxide film of the p-Si layer 160 on the upper surface S2 (FIG. 6) is removed. By removing the natural oxide film, the removal of the p-Si layer 160 is no longer inhibited by the natural oxide film, so that the etching of the p-Si layer 160 proceeds efficiently. Therefore, the amount of loss in the laminate can be suppressed. Furthermore, since the first wet etching is performed before the second wet etching, the removal of the natural oxide film is not inhibited by the foreign matter, so the etching progresses efficiently until the natural oxide film is removed. do. Therefore, the amount of loss can be further suppressed. Furthermore, by using the TMAH solution as the etching solution in the third wet etching, the p-Si layer 160 is etched with high selectivity. Therefore, the amount of loss can be further suppressed. From the above, wet etching for selectively removing the p-Si layer 160 from the object to be processed including the stack of the TEOS layer 150 and the SiN layer 140 and the p-Si layer 160 can partially remove the stack using CMP processing. When wet etching is performed after the removal step, the amount of loss of the laminate during wet etching can be sufficiently suppressed.

The second etching solution preferably has a temperature of 50°C or more and 80°C or less. Since the second etching solution has a temperature of 50° C. or more, the natural oxide film of the p-Si layer 160 can be easily removed by the second wet etching in as short a time as is usually desired in mass production. When the second etching solution has a temperature of 80° C. or less, the second etching solution can be easily handled.

The second etching solution is preferably aqueous ammonia in which ammonium hydroxide is dissolved in water in a mass ratio of 3 times or more and 10 times or less. Since ammonium hydroxide is dissolved in water at a mass ratio of three times or more, unintended damage in the second wet etching caused by an excessive concentration of ammonium hydroxide can be suppressed. can. Specifically, surface roughness caused by etching can be suppressed. In addition, excessive damage to areas other than the object to be treated can be easily suppressed. Moreover, the cost of the second etching solution can be suppressed. Since ammonium hydroxide is dissolved in water at a mass ratio of 10 times or less, it is easy to remove the natural oxide film of the p-Si layer 160 by the second wet etching in a short period of time that is usually desired in mass production. .

Next, the results of experiments conducted by the present inventors until they came up with the above embodiment will be described below.

Figure 8 shows the relationship between the etching amount (nm) of polysilicon (p-Si) by diluted ammonia water (dNH ₄ OH) and time (s) when the mass ratio NH ₄ OH:H ₂ O = 1:5 and When the temperature is 65°C, when the mass ratio NH ₄ OH:H ₂ O = 1:5 and the temperature is 40°C, when the mass ratio NH ₄ OH:H ₂ O = 1:100 and the temperature 65°C, and the mass It is a graph figure which shows the experimental result investigated about the case where ratio _NH4OH : _H2O =1:100 and the temperature of 40 degreeC. This result shows that the p-Si layer is etched at a high speed when the dNH ₄ OH concentration is relatively high (1:5) and the temperature is relatively high (65° C.). Note that even under these conditions, etching hardly progressed during the first 10 seconds, and it is thought that during this period, the etching of p-Si was inhibited by the natural oxide film of p-Si.

FIG. 9 is a graph showing the results of an experiment investigating the relationship between the etching amount and time of the p-Si layer, TEOS layer, and SiN layer using diluted ammonia water (dNH ₄ OH) having the above-mentioned conditions. Furthermore, FIG. 10 shows the experimental results of investigating the relationship between the etching amount and time of the p-Si layer, TEOS layer, and SiN layer using a TMAH aqueous solution with a mass ratio of TMAH:H ₂ O = 1:4 and a temperature of 80°C. It is a graph diagram. A comparison between FIGS. 9 and 10 shows that the TMAH solution is more preferable than dNH ₄ OH in order to efficiently etch the p-Si layer while suppressing the amount of loss in the TEOS layer and SiN layer as much as possible. Therefore, when the p-Si layer is actually being etched after the native oxide film and foreign matter on the p-Si layer have been removed, a TMAH solution is preferable to dNH ₄ OH as the etching solution. I understand that. Here, if the TMAH solution is used as an etching solution when the natural oxide film remains, the progress of etching will be inhibited by the natural oxide film. Therefore, it can be seen that wet etching with dNH ₄ OH is preferably performed prior to wet etching with TMAH solution. In view of this knowledge, the present inventors came up with the above-described embodiment.

Note that in the above description, the case where the silicon oxide layer and the silicon nitride layer are stacked in the in-plane direction of the substrate (the X direction in FIG. 2) in the stacked body has been described, but the silicon oxide layer and the silicon nitride layer They may be stacked in the direction (Z direction in FIG. 2). In this case as well, the same effect as described above can be obtained as long as each of the silicon oxide layer and the silicon nitride layer of the stack is exposed to the etching solution for etching the polysilicon layer.

Furthermore, although a case has been described in which the process in which the stack of silicon oxide layers and silicon nitride layers is partially removed (see FIGS. 5 and 6) is performed by CMP, the process is not limited to CMP. Any treatment that has at least one of a physical action and a chemical action is sufficient. For example, RIE (Reactive Ion Etching) has a feature in common with CMP in that it has both physical and chemical effects, and just as slurry residuals are a problem in CMP, RIE Adherence to the object to be processed becomes a problem. This deposit problem is resolved in the same way that the CMP slurry residual problem was resolved above.

<Embodiment 2>
FIG. 11 is a cross-sectional view schematically showing the configuration of the substrate processing apparatus 2 in the second embodiment.

The substrate processing apparatus 2 includes a box-shaped chamber 4 having an internal space, and a spin chuck that holds one substrate W horizontally within the chamber 4 and rotates it around a vertical rotation axis A1 passing through the center of the substrate W. 10, and a cylindrical processing cup 23 surrounding the spin chuck 10 around the rotation axis A1.

The chamber 4 includes a box-shaped partition wall 6 provided with a loading/unloading port 6b through which the substrate W passes, and a shutter 7 for opening/closing the loading/unloading port 6b. The chamber 4 further includes a rectifying plate 8 disposed below the air outlet 6 a that opens at the ceiling surface of the partition wall 6 . An FFU 5 (fan filter unit) that sends clean air (air filtered by a filter) is arranged above the air outlet 6a. An exhaust duct 9 for exhausting gas in the chamber 4 is connected to the processing cup 23. The air outlet 6 a is provided at the upper end of the chamber 4 , and the exhaust duct 9 is arranged at the lower end of the chamber 4 . A part of the exhaust duct 9 is arranged outside the chamber 4. The current plate 8 partitions the internal space of the partition wall 6 into an upper space Su above the current plate 8 and a lower space SL below the current plate 8. The upper space Su between the ceiling surface of the partition wall 6 and the upper surface of the rectifier plate 8 is a diffusion space in which clean air is diffused. The lower space SL between the lower surface of the current plate 8 and the floor surface of the partition wall 6 is a processing space in which substrates W are processed. The spin chuck 10 and the processing cup 23 are arranged in the lower space SL. The vertical distance from the floor of the partition wall 6 to the lower surface of the current plate 8 is longer than the vertical distance from the top surface of the current plate 8 to the ceiling surface of the partition wall 6. The FFU 5 sends clean air to the upper space Su via the air outlet 6a. The clean air supplied to the upper space Su hits the current plate 8 and diffuses the upper space Su. The clean air in the upper space Su passes through a plurality of through holes that vertically penetrate the current plate 8 and flows downward from the entire area of the current plate 8. The clean air supplied to the lower space SL is sucked into the processing cup 23 and exhausted from the lower end of the chamber 4 through the exhaust duct 9. Thereby, a uniform downward flow (downflow) of clean air flowing downward from the current plate 8 is formed in the lower space SL. Processing of the substrate W is performed in a state where a downward flow of clean air is formed.

The spin chuck 10 includes a disk-shaped spin base 12 held in a horizontal position, a plurality of chuck pins 11 that hold a substrate W in a horizontal position above the spin base 12, and a plurality of chuck pins 11 that hold a substrate W in a horizontal position above the spin base 12. It includes a spin shaft 13 that extends downward, and a spin motor 14 that rotates the spin base 12 and the plurality of chuck pins 11 by rotating the spin shaft 13. The spin chuck 10 is not limited to a clamping type chuck in which a plurality of chuck pins 11 are brought into contact with the outer circumferential surface of the substrate W, but also a chuck in which the back surface (lower surface) of the substrate W, which is a non-device forming surface, is attracted to the upper surface 12u of the spin base 12. Alternatively, a vacuum chuck that holds the substrate W horizontally may be used. Spin base 12 includes an upper surface 12u disposed below substrate W. The upper surface 12u of the spin base 12 is parallel to the lower surface of the substrate W. The upper surface 12u of the spin base 12 is a facing surface facing the lower surface of the substrate W. The upper surface 12u of the spin base 12 has an annular shape surrounding the rotation axis A1. The outer diameter of the upper surface 12u of the spin base 12 is larger than the outer diameter of the substrate W. The chuck pin 11 projects upward from the outer periphery of the upper surface 12u of the spin base 12. The chuck pin 11 is held by a spin base 12. The substrate W is held by the plurality of chuck pins 11 with the lower surface of the substrate W separated from the upper surface 12u of the spin base 12.

The substrate processing apparatus 2 includes a lower surface nozzle 15 that discharges a processing liquid toward the center of the lower surface of the substrate W. The lower surface nozzle 15 includes a nozzle disk portion disposed between the upper surface 12u of the spin base 12 and the lower surface of the substrate W, and a nozzle cylindrical portion extending downward from the nozzle disk portion. The liquid discharge port 15p of the lower surface nozzle 15 opens at the center of the upper surface of the nozzle disk portion. When the substrate W is held by the spin chuck 10, the liquid discharge port 15p of the lower surface nozzle 15 vertically faces the center of the lower surface of the substrate W. The substrate processing apparatus 2 includes a lower rinsing liquid pipe 16 that guides the rinsing liquid to the lower surface nozzle 15 and a lower rinsing liquid valve 17 interposed in the lower rinsing liquid pipe 16. When the lower rinsing liquid valve 17 is opened, the rinsing liquid guided by the lower rinsing liquid pipe 16 is discharged upward from the lower surface nozzle 15 and is supplied to the center of the lower surface of the substrate W. The rinsing liquid supplied to the lower nozzle 15 is pure water (deionized water: DIW). The rinsing liquid supplied to the lower nozzle 15 is not limited to pure water, but also includes IPA (isopropyl alcohol), carbonated water, electrolyzed ionized water, hydrogen water, ozone water, and hydrochloric acid water with a diluted concentration (for example, about 1 to 100 ppm). It may be either. Although not shown, the lower rinsing liquid valve 17 includes a valve body provided with an internal flow path through which liquid flows and an annular valve seat surrounding the internal flow path, a valve body that is movable with respect to the valve seat, and an actuator for moving the valve body between a closed position in which the body contacts the valve seat and an open position in which the valve body is spaced from the valve seat. The same applies to other valves. The actuator may be a pneumatic actuator or an electric actuator, or may be an actuator other than these. The control device 3 opens and closes the lower rinse liquid valve 17 by controlling an actuator.

The outer peripheral surface of the lower surface nozzle 15 and the inner peripheral surface of the spin base 12 form a lower cylindrical passage 19 that extends vertically. The lower cylindrical passage 19 includes a lower central opening 18 that opens at the center of the upper surface 12u of the spin base 12. The lower center opening 18 is arranged below the nozzle disk portion of the lower surface nozzle 15. The substrate processing apparatus 2 includes a lower gas pipe 20 that guides the inert gas supplied to the lower central opening 18 via the lower cylindrical passage 19, a lower gas valve 21 interposed in the lower gas pipe 20, and a lower gas A lower gas flow rate adjustment valve 22 is provided to change the flow rate of inert gas supplied from the piping 20 to the lower cylindrical passage 19. The inert gas supplied from the lower gas pipe 20 to the lower cylindrical passage 19 is nitrogen gas. The inert gas is not limited to nitrogen gas, but may be other inert gases such as helium gas or argon gas. These inert gases are low-oxygen gases having an oxygen concentration lower than that in air (approximately 21 vol%). When the lower gas valve 21 is opened, the nitrogen gas supplied from the lower gas pipe 20 to the lower cylindrical passage 19 is discharged upward from the lower central opening 18 at a flow rate corresponding to the opening degree of the lower gas flow rate adjustment valve 22. Ru. Thereafter, the nitrogen gas flows radially in the space between the lower surface of the substrate W and the upper surface 12u of the spin base 12 in all directions. As a result, the space between the substrate W and the spin base 12 is filled with nitrogen gas, and the oxygen concentration in the atmosphere is reduced. The oxygen concentration in the space between the substrate W and the spin base 12 is changed according to the opening degrees of the lower gas valve 21 and the lower gas flow rate adjustment valve 22. The lower gas valve 21 and the lower gas flow rate adjustment valve 22 are included in an atmosphere oxygen concentration changing unit that changes the oxygen concentration in the atmosphere in contact with the substrate W.

The processing cup 23 includes a plurality of guards 25 for receiving the liquid discharged outward from the substrate W, a plurality of cups 26 for receiving the liquid guided downward by the plurality of guards 25, and a plurality of guards 25 and a plurality of cups. 26 and a cylindrical outer wall member 24 surrounding the outer wall member 26. FIG. 11 shows an example in which two guards 25 and two cups 26 are provided. The guard 25 includes a cylindrical guard cylindrical portion 25b surrounding the spin chuck 10, and an annular guard ceiling portion 25a extending obliquely upward toward the rotation axis A1 from the upper end of the guard cylindrical portion 25b. The plurality of guard ceiling parts 25a are vertically overlapped, and the plurality of guard cylindrical parts 25b are arranged concentrically. The plurality of cups 26 are respectively arranged below the plurality of guard cylindrical parts 25b. The cup 26 forms an annular liquid receiving groove that opens upward. The substrate processing apparatus 2 includes a guard lifting unit 27 that lifts and lowers a plurality of guards 25 individually. The guard elevating unit 27 positions the guard 25 at any position from the upper position to the lower position. The upper position is a position where the upper end 25u of the guard 25 is placed above the holding position where the substrate W held by the spin chuck 10 is placed. The lower position is a position where the upper end 25u of the guard 25 is located below the holding position. The annular upper end of the guard ceiling portion 25a corresponds to the upper end 25u of the guard 25. The upper end 25u of the guard 25 surrounds the substrate W and the spin base 12 in plan view. When the processing liquid is supplied to the substrate W while the spin chuck 10 is rotating the substrate W, the processing liquid supplied to the substrate W is shaken off from the substrate W. When the processing liquid is supplied to the substrate W, the upper end 25u of at least one guard 25 is arranged above the substrate W. Therefore, a processing liquid such as a chemical liquid or a rinsing liquid discharged from the substrate W is received by one of the guards 25 and guided to the cup 26 corresponding to this guard 25.

The center nozzle 45 has a liquid discharge port that discharges liquid. The center nozzle 45 has an opening at its lower end through which the liquid supplied from the liquid preparation unit 52 via the liquid valve 53 is discharged. When the liquid valve 53 is opened, the liquid prepared by the liquid preparation unit 52 is supplied onto the upper surface of the substrate W by being discharged downward from the center nozzle 45. The liquid preparation unit 52 is supplied with a TMAH solution supply source, an NH ₄ OH aqueous solution (ammonia aqueous solution) supply source, an H ₂ O ₂ supply source, and a DIW via valves 51T, 51N, 51H, and 51D, respectively. Source is connected. The liquid preparation unit 52 can prepare a TMAH solution by opening the valve 51T, and at this time, can adjust the concentration of the solution by adjusting the opening degree of the valve 51D. Further, the liquid preparation unit 52 can prepare the NH ₄ OH aqueous solution by opening the valve 51N, and at that time, adjust the concentration of the NH ₄ OH aqueous solution as the diluted ammonia water by adjusting the opening degree of the valve 51D. Can be adjusted. Further, the liquid preparation unit 52 can prepare SC1 (mixed aqueous solution of NH ₄ OH and H ₂ O ₂ ) by opening the valve 51N and the valve 51H, and at that time, by adjusting the opening degree of the valve 51D. The concentration of the solution can be adjusted. Furthermore, the liquid preparation unit 52 can prepare DIW as a rinse liquid by opening the valve 51D.

FIG. 12 is a cross-sectional view schematically showing the structure of the substrate W before and after the substrate processing method according to the second embodiment is performed. The left side of FIG. 12 shows a cross section of the substrate W before the process (etching) shown in FIG. 13 is performed, and the right side of FIG. 12 shows the cross section of the substrate W after the process (etching) shown in FIG. It shows a cross section of. As shown on the right side of FIG. 12, when the substrate W is etched, a plurality of recesses R1 recessed in the surface direction of the substrate W (direction perpendicular to the thickness direction Dt of the substrate W) are formed on the inner surface 92s (side surface) of the recess 92. is formed.

As shown in FIG. 12, the substrate W has a laminate 91 formed on a base material such as a silicon wafer. Laminated body 91 includes a plurality of polysilicon layers P1 to P3 and a plurality of silicon oxide layers O1 to O3. The plurality of polysilicon layers P1 to P3 and the plurality of silicon oxide layers O1 to O3 are stacked in the thickness direction Dt of the substrate W such that the polysilicon layers P1 to P3 and the silicon oxide layers O1 to O3 are alternately replaced. . The polysilicon layers P1 to P3 are thin films that have undergone a deposition process of depositing polysilicon on the substrate W and a heat treatment process of heating the deposited polysilicon (see FIG. 13). Note that the heat treatment step may be omitted.

The laminate 91 has a recess 92 recessed from the outermost surface Ws of the substrate W in the thickness direction Dt of the substrate W (direction perpendicular to the surface of the base material of the substrate W). The recess 92 penetrates the plurality of polysilicon layers P1 to P3 and the plurality of silicon oxide layers O1 to O3 in the thickness direction Dt of the substrate W. The side surfaces of the polysilicon layers P1 to P3 and the silicon oxide layers O1 to O3 are exposed at the inner surface 92s of the recess 92. The recess 92 may be any one of a trench, a via hole, and a contact hole, or may be other than these. The recess 92 is formed by dry etching (see FIG. 13). Dry etching is accompanied by the generation of etching residue. Here, the etching that involves generation of etching residue for forming the recess 92 is not limited to dry etching, and includes, for example, etching using a liquid.

Before the process (etching) shown in FIG. 13 is started, a natural oxide film as a surface oxide film is normally formed on the surface layers of the polysilicon layers P1 to P3 and the silicon oxide layers O1 to O3. Further, etching residues generated when forming the recesses 92 are usually attached to the surface layers of the polysilicon layers P1 to P3 and the silicon oxide layers O1 to O3. The two-dot chain line on the left side of FIG. 12 schematically shows the contours of these surface oxide films and etching residues.

FIG. 13 is a flow diagram for explaining the substrate processing method in the second embodiment. In the substrate processing apparatus 2, the steps after "start" in FIG. 13 are executed.

When the substrate W is processed by the substrate processing apparatus 2, a loading process of loading the substrate W into the chamber 4 is performed (step S11 in FIG. 13). Specifically, with all the guards 25 in the lower position, a hand (not shown) of a central robot (not shown) supports the substrate W and causes it to enter the chamber 4. Then, the center robot places the substrate W on the hand on the plurality of chuck pins 11 with the surface of the substrate W facing upward. Thereafter, the plurality of chuck pins 11 are pressed against the outer peripheral surface of the substrate W, and the substrate W is gripped. After placing the substrate W on the spin chuck 10, the central robot withdraws the hand from inside the chamber 4.

Next, by opening the lower gas valve 21, the lower central opening 18 of the spin base 12 starts discharging nitrogen gas. Thereby, the oxygen concentration in the atmosphere in contact with the substrate W is reduced. Further, the guard lifting unit 27 raises one of the guards 25 from the lower position to the upper position. Thereafter, the spin motor 14 is driven and rotation of the substrate W is started (step S12 in FIG. 13).

Next, a step of supplying the removal liquid to the upper surface of the substrate W is performed (step S13 in FIG. 13). As a result, the removal liquid is supplied to the recess 92, thereby removing the etching residue attached to the inner surface 92s of the recess. A TMAH solution or SC1 may be used as the removal liquid. Specifically, the removal liquid discharged from the center nozzle 45 collides with the center of the upper surface of the substrate W, and then flows outward along the upper surface of the rotating substrate W. As a result, a liquid film of the removal liquid covering the entire upper surface of the substrate W is formed, and the removal liquid is supplied to the entire upper surface of the substrate W. After a predetermined period of time has elapsed, the discharge of the removal liquid is stopped. Note that, due to this step S13, a surface oxide film may be newly or additionally formed on the surface layer of the polysilicon layers P1 to P3. Note that the same TMAH solution or SC1 as in step S151 (FIG. 3: Embodiment 1) may be used as the removal liquid.

Next, a first etching step is performed in which diluted ammonia water (ammonia aqueous solution) as a first etching solution is supplied onto the upper surface of the substrate W (step S14 in FIG. 13). As a result, the ammonia aqueous solution is supplied to the recess 92, thereby etching the surface oxide film formed on the polysilicon layers P1 to P3 at or before step S13. Specifically, the ammonia aqueous solution discharged from the center nozzle 45 collides with the center of the upper surface of the substrate W, and then flows outward along the upper surface of the rotating substrate W. As a result, a liquid film of ammonia aqueous solution covering the entire upper surface of the substrate W is formed, and the ammonia aqueous solution is supplied to the entire upper surface of the substrate W. After a predetermined period of time has elapsed, the discharge of the ammonia aqueous solution is stopped. Note that as the diluted ammonia water, the same one as in step S152 (FIG. 3: Embodiment 1) may be used.

Next, a second etching step is performed in which a TMAH solution as a second etching solution is supplied onto the upper surface of the substrate W (step S15 in FIG. 13). This supplies the TMAH solution to the recess 92, thereby etching the polysilicon layers P1 to P3 at a higher etching rate than the silicon oxide layers O1 to O3. In other words, polysilicon layers P1 to P3 are selectively etched. Specifically, the TMAH solution discharged from the center nozzle 45 collides with the center of the upper surface of the substrate W, and then flows outward along the upper surface of the rotating substrate W. As a result, a liquid film of the TMAH solution covering the entire upper surface of the substrate W is formed, and the TMAH solution is supplied to the entire upper surface of the substrate W. Before the discharge of the second etching liquid is started, the guard lifting/lowering unit 27 may vertically move at least one guard 25 in order to switch the guard 25 that receives the liquid discharged from the substrate W. After a predetermined period of time has elapsed, the ejection of the TMAH solution is stopped. Note that the same TMAH solution as in step S153 (FIG. 3: Embodiment 1) may be used.

Next, a rinsing liquid supply step is performed in which DIW as a rinsing liquid is supplied onto the upper surface of the substrate W (step S16 in FIG. 13). Specifically, the DIW discharged from the center nozzle 45 collides with the center of the upper surface of the substrate W, and then flows outward along the upper surface of the rotating substrate W. The second etching liquid on the substrate W is washed away by DIW discharged from the center nozzle 45. As a result, a DIW liquid film covering the entire upper surface of the substrate W is formed. After a predetermined period of time has elapsed, the discharge of DIW is stopped.

Next, a drying process is performed in which the substrate W is dried by rotating the substrate W (step S17 in FIG. 13). Specifically, the spin motor 14 accelerates the substrate W in the rotational direction, and rotates the substrate W at a high rotational speed (for example, several thousand rpm) that is higher than the rotational speed of the substrate W during the period from steps S13 to S15. As a result, the liquid is removed from the substrate W, and the substrate W is dried. When a predetermined period of time has elapsed after the high-speed rotation of the substrate W was started, the spin motor 14 stops rotating. As a result, the rotation of the substrate W is stopped (step S18 in FIG. 13).

Next, an unloading step is performed to unload the substrate W from the chamber 4 (step S19 in FIG. 13). Specifically, the guard lifting unit 27 lowers all the guards 25 to the lower position. Further, by closing the lower gas valve 21, the lower central opening 18 of the spin base 12 stops discharging nitrogen gas. Thereafter, the central robot (not shown) moves a hand (not shown) into the chamber 4. After the plurality of chuck pins 11 release the grip on the substrate W, the center robot supports the substrate W on the spin chuck 10 with its hand. Thereafter, the central robot supports the substrate W with the hand and withdraws the hand from inside the chamber 4. Thereby, the processed substrate W is carried out from the chamber 4.

According to this embodiment, etching residues generated by dry etching are removed in step S13, which is performed prior to etching the polysilicon layers P1 to P3 in step S15. Furthermore, the surface oxide films of the polysilicon layers P1 to P3 are removed in step S14, which is performed prior to the etching of the polysilicon layers P1 to P3 in step S15. By removing the surface oxide film, the removal of the polysilicon layers P1 to P3 is no longer inhibited by the surface oxide film, so that etching of the polysilicon layers P1 to P3 proceeds efficiently. Therefore, the amount of loss in the silicon oxide layers O1 to O3 can be suppressed. Furthermore, since step S13 is performed before step S14, the removal of the surface oxide film is not inhibited by etching residue, so that the etching progresses efficiently until the surface oxide film is removed. Therefore, the amount of loss can be further suppressed. Furthermore, by using the TMAH solution as the etching solution in step S15, polysilicon is etched with high selectivity. Therefore, the amount of loss can be further suppressed. From the above, after the process of forming recesses 92 in the stacked body 91 of silicon oxide layers O1 to O3 and polysilicon layers P1 to P3 by dry etching, wet etching is performed to selectively remove polysilicon in recesses 92. In this case, the amount of loss of silicon oxide layers O1 to O3 during wet etching can be sufficiently suppressed.

By continuously performing steps S13 to S15, it is possible to efficiently process the substrate. Since steps S13 to S15 are performed continuously in this way, a rinsing process such as step S16 cannot be interposed between steps S13 to S15, but steps S13 to S15 all use ammonia-based processing liquid. Since it is used, the adverse effects from the previous process are small even if there is no rinsing process between processes. Therefore, efficient substrate processing is realized as described above.

<Modification 1>
Note that in the above, a TMAH solution is used as a suitable etching solution in step S15, but the etching solution in step S15 is not limited to the TMAH solution, and may be any quaternary ammonium hydroxide solution. The solvent for the quaternary ammonium hydroxide solution may be water (H ₂ O). Quaternary ammonium hydroxides include TMAH, TBAH (tetrabutylammonium hydroxide), TPeAH (tetrapentylammonium hydroxide), THAH (tetrahexylammonium hydroxide), TEAH (tetraethylammonium hydroxide), and TPAH (tetraethylammonium hydroxide). propylammonium hydroxide), or may be other than these. All of these are included in organic alkalis.

<Modification 2>
In this modification, diluted ammonia having a higher ammonia concentration than the diluted ammonia water (ammonia aqueous solution) used as the first etching solution (step S14 (FIG. 13)) is used as the second etching solution (step S15 (FIG. 13)). Water is used. According to this modification, etching residues generated by dry etching are removed in step S13, which is performed prior to etching the polysilicon layers P1 to P3 in step S15. Furthermore, the surface oxide films of the polysilicon layers P1 to P3 are removed in step S14, which is performed prior to the etching of the polysilicon layers P1 to P3 in step S15. By removing the surface oxide film, the removal of the polysilicon layers P1 to P3 is no longer inhibited by the surface oxide film, so that etching of the polysilicon layers P1 to P3 proceeds efficiently. Therefore, the amount of loss in the silicon oxide layers O1 to O3 can be suppressed. Furthermore, since step S13 is performed before step S14, the removal of the surface oxide film is not inhibited by etching residue, so that the etching progresses efficiently until the surface oxide film is removed. Therefore, the amount of loss can be further suppressed. Further, by using diluted ammonia water having a higher ammonia concentration than the diluted ammonia water used in step S14 as the etching solution in step S15, polysilicon can be etched sufficiently efficiently. From the above, after the step of forming the recesses 92 in the stacked body 91 of the silicon oxide layers O1 to O3 and the polysilicon layers P1 to P3 by dry etching, wet etching is performed to efficiently and selectively remove polysilicon in the recesses 92. In the case where wet etching is performed, the amount of loss of silicon oxide layers O1 to O3 during wet etching can be sufficiently suppressed.

Although this invention has been described in detail, the above description is illustrative in all aspects, and the invention is not limited thereto. It is understood that countless variations not illustrated can be envisaged without departing from the scope of the invention. The configurations described in each of the above embodiments and modifications can be appropriately combined or omitted as long as they do not contradict each other.

O1 to O3: Silicon oxide layer P1 to P3: Polysilicon layer R1: Recess S1: Top surface S2: Top surface 2: Substrate processing device 91: Laminated body 92: Concave portion 92s: Inner surface 110: Substrate 111: Base portion 112: Fin portion 120: Impurity region 121: Main part 122: Extension part 130: Insulated gate structure 131: Gate insulating film 132: Gate electrode 140: SiN layer (silicon nitride layer)
150: TEOS layer (silicon oxide layer)
160: p-Si layer (polysilicon layer)

Claims (6)

A method of etching a workpiece including a stack of silicon oxide layers and silicon nitride layers, and a polysilicon layer, the method comprising:
(a) partially removing the laminate by a process having at least one of a physical action and a chemical action;
(b) exposing the object to be treated to a mixed aqueous solution of ammonium hydroxide and hydrogen peroxide or a tetramethylammonium hydroxide solution as a first etching solution;
(c) after the step (b), exposing the object to aqueous ammonia as a second etching solution;
(d) after the step (c), etching the polysilicon layer by exposing the object to be treated to a tetramethylammonium hydroxide solution as a third etching solution;
An etching method comprising: The etching method according to claim 1, wherein the second etching solution has a temperature of 50°C or more and 80°C or less. 3. The etching method according to claim 1, wherein the second etching solution is aqueous ammonia in which ammonium hydroxide is dissolved in water in a mass ratio of 3 to 10 times. A substrate processing method for a substrate including a laminate of a silicon oxide layer and a polysilicon layer and having a recess formed in the laminate by etching that generates etching residue, the recess being formed by the oxidation The substrate processing method includes: a silicon layer and an inner surface exposing the polysilicon layer;
(a) removing the etching residue attached to the inner surface of the recess by supplying a removal liquid into the recess;
(b) After the step (a), a first etching step of etching the surface oxide film formed on the polysilicon layer in the step (a) or before by supplying an ammonia aqueous solution into the recess. and,
(c) After the step (b), a second step of etching the polysilicon layer at a higher etching rate than the silicon oxide layer by supplying a quaternary ammonium hydroxide solution into the recess. etching process and
A substrate processing method comprising: A substrate processing method for a substrate including a laminate of a silicon oxide layer and a polysilicon layer and having a recess formed in the laminate by etching that generates etching residue, the recess being formed by the oxidation The substrate processing method includes: a silicon layer and an inner surface exposing the polysilicon layer;
(a) removing the etching residue attached to the inner surface of the recess by supplying a removal liquid into the recess;
(b) After the step (a), a first etching step of etching the surface oxide film formed on the polysilicon layer in the step (a) or before by supplying an ammonia aqueous solution into the recess. and,
(c) After the step (b), by supplying into the recess an ammonia aqueous solution having a higher ammonia concentration than the ammonia aqueous solution in the step (b), the polysilicon layer is a second etching step of etching at a high etching rate;
A substrate processing method comprising: 6. The substrate processing method according to claim 4, wherein the steps (a) to (c) are performed continuously.

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